In the design of at least certain structures, it may be desirable to measure the stiffness of the structure. One way to measure the stiffness includes providing a static load on the structure and measuring the linear deflection of the structure at the load point with a string pot. This permits measurement of the so-called static stiffness of the structure. However, such static testing does not give insight into the dynamic stiffness of the structure, such as when the structure is acted upon by, for example, low frequency dynamic loads. The dynamic stiffness may vary from the static stiffness, and the dynamic stiffness may vary over different frequencies of dynamic loads.